It is known that, in order to effect a microbiological analysis of air, use is generally made of a sampling apparatus for depositing microorganisms, such as bacteria, yeasts or molds, present in an air sample, on a layer of growth media, such as growth media, in a receptacle, and then this receptacle is incubated at the required temperature and for the required length of time to enable the deposited microorganisms to develop in the form of colonies visible to the naked eye, so that they can be counted and identified.